This is a fairly late update, but closing the loop on this: I believe the 3-10% number ended up being the secondary attack rate among households where the infected person was isolated after diagnosis. So that’s an estimate of the rate of transmission during extended close contact before symptoms/​diagnosis, not after, which makes more sense. I assume that extended close contact with a symptomatic infected person will result in very likely transmission.
This is a fairly late update, but closing the loop on this: I believe the 3-10% number ended up being the secondary attack rate among households where the infected person was isolated after diagnosis. So that’s an estimate of the rate of transmission during extended close contact before symptoms/​diagnosis, not after, which makes more sense. I assume that extended close contact with a symptomatic infected person will result in very likely transmission.